I've had lockers hanging in my gear room for years and gravity has yet to unscrew. But from now on I'll check them every day and I'll be sure to let this forum know if I observe any movement in the sleeves.

Check them after the 5.8 quake.

Nevermind, you're too far out in left field to have felt it.

But for those with a more rational mindset, it's the combination of gravity and the continual vibration from rope moving over metal that causes the screw sleeve to unscrew.

Can it happen against gravity? You betcha. But it's more likely to happen with gravity.

Me thinks the word "we" is being used a little too freely in these parts.

I agree:

hugepedro wrote:

No, the primary reason we use 2 biners is for strength and redundancy.

rescueman wrote:

The primary reason we still use two 'biners at the top rope anchor is to increase the bend radius of the rope and reduce the internal friction from falling or lowering over a tight radius (bend radius is ideally at least 4x rope diameter).

as a comparative risk in climbing, this whole topic utterly pales compared to the lack of craft and attentiveness in belaying.

Couldn't agree more.

I witnessed a young woman sitting on the ground with her back against a tree, chatting with her friends as she belayed her partner at the Gunks. He took a 30' fall to ground and his belayer didn't seem to notice until he landed between her legs.

Then the first thing she did (after screaming) was lift him up to hug him (putting his spine at risk). He was evacuated by the climbing rangers and transported to the hospital with a spinal injury.

It's for this reason that I wrote an article for Technical Rescue magazine in 2004 called Is Fail-Safe Really Safe? about the almost universal rush among rescue teams toward auto-locking belay devices, such as the Petzl I'D and the Traverse Rescue 540. In the sport climbing world, it's the GriGri.

The problems with relying on technology to prevent disaster are two-fold: 1) the more complex the technology the more potential failure modes 2) reliance on equipment often results in a decrease in attentiveness and craft

The latter is an outcome of what I called the “complacency tendency” and the “distraction factor”.

The KISS principle combined with attention and care is the best approach to safety in almost every field.

The primary reason we still use two 'biners at the top rope anchor is to increase the bend radius of the rope and reduce the internal friction from falling or lowering over a tight radius (bend radius is ideally at least 4x rope diameter).

You were proven wrong on that one too, Mr. 9knAtTheBelay.

Hardly.

Read Titt's report Belay Device Theory, which states that a tight radius bend, such as around a single carabiner, causes strands of rope fiber to exceed their elastic limit.

And read the recommendations of every rope manufacturer about recommended sheave diameter to protect the rope from damage.

But, I suppose that a hot shot climber who has no problem recommending to beginners that they ignore manufacturer warnings against tri-axial loading of carabiners would also recommend ignoring manufacturer warnings against small-diameter capstans.

One of the commonly quoted rules for toproped climbing is that one should always use two opposite and opposed lockers at the master point.

The idea is that there is no way that the rope could possibly jump out of two opposite and opposed lockers. And while it may be possible -- however unlikely -- for movement in the system to cause the one of the gates to become unlocked and to open, it would be nearly impossible for the both lockers to become unlocked and to be opened.

In the guiding world, two opposite and opposed lockers are considered to be industry standard. The liklihood of a single locking carabiner becoming unlocked and opening is incredibly low. However, this is one of the rules that you learn when you start to climb and it has become so integral to outdoor groups throughout the world in toproping that it has become the industry standard across the board.

Industry standard is one of those phrases that we should pay attention to in climbing. There are very few things that can be considered industry standard in the climbing world.

its not "unsafe" or even any "less safe" ... if it was all the guiding companies here wouldnt be using 2 opposed lockers for their clients ...

but then what do they know ... theyre obviously not "rescue professionals"

No, the question is why are you continuing your deliberate avoidance of the point of this discussion and repeating ad nauseam the mantra of O&O in every situation - particularly when every pictorial example you've shown is with free-hanging biners.

I've stated clearly that O&O is not a problem when the biners are hanging in air - and that they MAY be problematic when the biners are leaning on the rock.

This is a classic straw man argument that you repeat ad infinitum, since it is based on a complete distortion of my statements.

Your quoted source has the same approach as I:

American Alpine Institute wrote:

Rules in climbing exist to create a wide margin of safety. There's really no reason at all not to have a wide margin of safety in a toproped environment.

Safety requires determining the best configuration for each application - not using rote "rules" in every situation.

One of the reasons that my rigging & rescue training always receives such superlative feedback is that, unlike most instructors who teach rules (such as, in Fire Service rescue: never use a bowline for life safety - always a figure-8 on a bight or follow-through), I teach principles - the "why" behind the "how".

I teach my students to use their brains to choose the best rigging tools from the toolbox, and give them an extensive toolbox of options to choose from, demonstrating the specific applications, advantages and disadvantages for each.

In most circumstances O&O top rope anchor biners are fine - in a few cases, they're problematic and potentially less safe.

But if you're more comfortable with repeating Gospel and living by the ONE AND ONLY WAY, then the world is worse off for your presence. Perhaps you'll be taken up by the next scheduled Rapture.

i used to o&o lockers when i was doing more TR. then one day i get to the top and noticed that they rubbed together and unlocked. i figured i just didn't spin the lock down firmly enough... that is until [at a later point] i saw the same thing happen and one pushing the gate of the other slightly open. i have never used 2 lockers as in the masterpoint since; and despite that being anecdotal evidence (with n=1), i don't suggest that anyone else do it either.

then there's the whole argument of torsional effects, but i'm not interested in validating/testing that argument.

2 o&o non-lockers is plenty and has never failed me or caused any of the aforementioned problems.

The primary reason we still use two 'biners at the top rope anchor is to increase the bend radius of the rope and reduce the internal friction from falling or lowering over a tight radius (bend radius is ideally at least 4x rope diameter).

I have a hard time getting excited about this when I think of how many raps / lowerings a rope sees in its life. An ATC puts a pretty wicked bend in the rope.

But I continue to assert that the reason we use two carabiners in a top rope belay, even when no longer needed for security, is to increase the overall bend radius (effective sheave diameter) and decrease the probability of damaging the rope fibers.

No way! The master point on a TR is a single point of catastrophic failure of the system. The amount of motion at that point and the fact that it is unattended is the real reason it often receives two carabiners. Carabiners connecting belay/rappel devices can be checked and managed by the user. A toprope anchor master point cannot. It could be a misguided attempt to avoid friction for you but everyone else I have ever met who uses two opposed biners does so to prevent any event that could free the rope from the system. An experienced climber can understand when two biners are superflous or supersitious. Beginners should continue to learn rules that will ultimately contribute to an increased level of safety in situations they cannot properly judge. Through experience everyone learns why rules can be bent or broken.

i used to o&o lockers when i was doing more TR. then one day i get to the top and noticed that they rubbed together and unlocked...2 o&o non-lockers is plenty and has never failed me or caused any of the aforementioned problems.

Thanks for the anecdotal evidence that I might actually have a point that everyone else fails to appreciate.

This is not an uncommon outcome when we take a traditionally good idea - O&O non-lockers - and simply assume that we can apply the same approach to new technology - screw-lock biners - without thinking through the consequences.

The history of the "advance" of technology is a history of unintended consequences, and every "solution" creates yet another set of problems that requires yet another "solution".

The primary reason we still use two 'biners at the top rope anchor is to increase the bend radius of the rope and reduce the internal friction from falling or lowering over a tight radius (bend radius is ideally at least 4x rope diameter).

You were proven wrong on that one too, Mr. 9knAtTheBelay.

Hardly.

Read Titt's report Belay Device Theory, which states that a tight radius bend, such as around a single carabiner, causes strands of rope fiber to exceed their elastic limit.

And read the recommendations of every rope manufacturer about recommended sheave diameter to protect the rope from damage.

But, I suppose that a hot shot climber who has no problem recommending to beginners that they ignore manufacturer warnings against tri-axial loading of carabiners would also recommend ignoring manufacturer warnings against small-diameter capstans.

Ropes are used under load over single-biner radius bends all the time. Rapping. Lowering. Falling. Hanging when working routes. Ropes are disposable items, as are most climbing gear. No matter how they get worn, it’s up to us to assess their fitness for use and retire them when appropriate.

If you really think that rope wear is the primary reason for using 2 biners at the anchor, and not the more immediate risk of a single biner being compromised, then you are a bigger climbing dumbass than I thought. And your grasp of risk management, in which you like to portray yourself as knowledgeable, is questionable.

And for the umpteenth time, that argument wasn’t about manufacturer warnings, it was about whether the AMGA anchor rig was unsafe. You lost that argument a long time ago. It’s a pity you didn’t also salvage some of your integrity by owning up to your errors, instead of trying to save face.

The master point on a TR is a single point of catastrophic failure of the system.

Actually, the most common single point of catastrophic failure is the rope (it easily cuts on a sharp edge, regardless of its extraordinary tensile strength), and yet we never top-rope on twin ropes.

We use a single harness, a single tie-in knot, a single belay device attached to a single carabiner, and - even in some institutional settings (such as the Outward Bound school where I worked) we typically used a single tree and a single loop of webbing as a top-rope anchor - to support the climber, the belayer, a back-up belayer (using body belays), and an instructor.

Many years with millions of user hours and zero failures.

But I never argued against using two biners at the anchor master point. Just advocated using them intelligently.

You may not have argued against using two carabiners but you did incorrectly identify the reason for their use as being more about friction than security. Climbers make regular use of directionals to reduce the possibility of severing/damaging the rope but in some situations where this cannot be properly mitigated use a twin/half rope setup. Noobs may not TR at a crag on halfs, but plenty of people second a leader (essentially TRing) who has climbed on half ropes. Rope severing flakes/edges are usually a more obvious hazard to beginners. The issue is really about understanding how systems work, change and fail; the factors that contribute to odd/surprising/catastrophic behavior of system and their likelihood. Many beginners simply cannot understand that bump on a vertical wall could open a locking carabiner and because of that are admonished to use two biners.

Under proper use harnesses, knots, belay devices and carabiners do not fail. There is no logical reason to treat them as suspect.

opposed lockers that still for some reason "unlock" are still opposed ... unopposed lockers that someone has forgotten to lock are definately not "safe" (and everyone has forgotten or caught someone who forgot to lock their lockers, if they claim they havent, well make yr own judgment about that persons truthfulness)

who would you rather listen to .... some "rescue professional" whos always right

or AAI, mr long, and guides .... for newbs, next time you take a course with a guide ... ask them if opposed lockers are "unsafe" and look at what they set up for you for TR

chances are, theyll be opposed lockers

of course i expect a whole bunch of yadda yadda yadda from the "rescue expert" about how unsafe they are ... but then he "knows" whats best for ya even from over the intrawebs

It's a pity that you long ago gave up having an intellectually honest (and mature) debate, and persist with the sole purpose of trashing everything I post.

You sure whine a lot for someone that fired the first flame salvo in both of these threads. Grow some sack, dude. I'm not trashing everything you post, I'm pointing out obvious factual errors of someone that sprays all day about his qualifications and experience, as though that makes him infallible. Sorry to hurt your feelings, man, but if you're going to post stupid shit you're going to get called on it. And I'm not the only person calling you on this crap, so you might want to consider rethinking some of this shit rather than puffing out your chest even further. Just sayin.

Yes, I know that you don't think much of Attaway's friction formulae. And you also acknowledge the math is far too complicated for even the great Titt to come up with a unified theory of everything.

I'll accept your theory. I measure (with crude instrumentation) a 12% increase in friction going from a single carabiner to two.

But I continue to assert that the reason we use two carabiners in a top rope belay, even when no longer needed for security, is to increase the overall bend radius (effective sheave diameter) and decrease the probability of damaging the rope fibers.